This application is designed to provide for didactic and research training for four predoctoral and six postdoctoral trainees annually in the problems and methods of interdisciplinary research in mental retardation and developmental disabilities (MRDD). Training will primarily take place in laboratories and field settings of the six major research groups at the UCLA Mental Retardation Research Center (MRRC): Molecular and Developmental Neuroscience, Neurobiochemistry and Molecular Genetics, Systems Neuroscience, Plasticity and Behavior, Sociobehavior, and Developmental Disabilities Clinical Research. MRRC faculty members approach problems in MRDD from a number of different disciplinary viewpoints supported by nine scientific and service core facilities funded by an NICHD Center Core Grant as well as University support. This problem-oriented and interdisciplinary approach will be emphasized in the formal didactic training program. The MRRC faculty has undergone an extensive renewal during the last several years, a number of them retired or left, and thirteen new faculty members were recruited to the MRRC from outside or from campus departments. The three highest priority areas for development at UCLA School of Medicine are: neuroscience, human genetics, and aging. A Department of Human Genetics has been formed, and a new Neuroscience and Human Genetics Research Building has opened. These will provide for enriching the MRRC research and training relevant to MRDD. A designed program of classes and seminars will serve 1) to introduce the research trainees to the nature and range of problems in the area of mental retardation and developmental disabilities; 2) to facilitate trainees with access to the ideas and methods of disciplines other than their own; 3) to provide forums for initiating cross-disciplinary discussion, and 4) to enable trainees to extend their knowledge in their own fields of specialization. Postdoctoral candidates must have Ph.D.s in relevant discipline or have M.D.s and intend to devote their careers to biomedical research. Predoctoral candidates will have been accepted as graduate students in Ph.D. programs in which members of the MRRC are affiliated. Predoctoral candidates will have completed one or more years of graduate education. It is anticipated that trainees will pursue research careers that focus on mental retardation or related developmental problems. They will assume positions in medical schools, in research institutes and hospitals, and in traditional academic departments.